Substituted piperidines



United States Patent F P 2,833,775 1C v Patented May 6, 1958 SUBSTITUTED PIPERIDINES Nathan Sperber, Bloomfield, Frank Villani, Cedar Grove, and Domenick Papa, Bloomfield, N. J., assignors to Schering Corporation, Bloomfield, N. J., a corporation of New Jersey No Drawing. Original application August 17, 1951, Se-

rial No. 242,438, now Patent No. 2,739,968, dated March 27, 1Q56. Divided and this application August 22, 1955, Serial No. 529,902

Claims. (Cl. 260-2945) This invention relates to a new group of compounds .of important physiological properties. More particularly, the invention relates to substituted piperidines having antihistaminic, antispasmodic, antiacetylcholine and analgesic activity, to intermediates for preparing them, and to methods of preparing them.

The substituted piperidines of'this invention may be represented by the general formula ROBE wherein R and R are members of the group consisting of aryl, aralkyl, cycloalkyl, cycloalkene, heterocyclic and alkyl groups, R is selected from the group consisting of hydrogen, lower alkyl and aralkyl groups, and R is selected from the group consisting of hydrogen, chlorine, bromine, lower alkyl and lower alkoxy groups. Representative of the groups R and R are phenyl, benzyl, thienyl, pyridyl, pyrimidyl, thiazyl, furyl, cyclohexyl, cyclohexenyl, propyl, isopropyl, butyl and others of these general types as well as their dialkylarnino, lower alkoxy and lower alkyl substitution products. This invention also embraces the acid addition salts and the quaternary salts of the compounds of the general formula.

In general, the compounds of the present invention may be prepared by several methods. The most general procedure is that illustrated by the following series of equations for the specific compounds shown:

poon 00011 00011 0001 7 H2 HCHO soon I an r HO 0 on A1013 \N/ 11 17.1101 r .Hol'

H01 H01 CH3 on; 1 11 III IV R\ /R1 R\ R1 COR o-orr o o RrHfil w H20 H3 -----7 Li; Mg N/ N/ r N N/ I l l 1 CH3 CH3 CH3 CH3 V VI VII vm Pyridinecarboxylic acids such as picolinic acid, nicotinic acid, 6-methylnicotinic acid, 'etc., as such, or in the form of their hydrochlorides,.are readily reducible to the corresponding piperidinecarboxylic acids. This reaction is carried out in a low pressure hydrogenator using platinum oxide catalyst or by high pressure hydrogenation using Raney nickel catalyst. Methylation of the piperidine compound proceeds smoothly by any of the known methods (for example, formic acid and formaldehyde) and subsequent treatment of the N-methyl compound with thionyl chloride gives the corresponding acid chloride. Reaction 2 of the acid chloride by any of the usual Friedel-Craf-ts procedures with an aromatic compound, for example, benzene, thiophene, chlorobenzene, methoxybenzene, ctc., yields the keto compounds of type V. Treatment of the latter substance with an organometallic derivative of a halogenated thiophene, pyridine, pyrimidine, thiazole, furan, cycloalkyl or alkyl compound yields the tertiary carbinols of Formula VI. These substances are for the most part high-boiling liquids which can be readily recrystallized to white crystalline solid. Dehydration of the tertiary carbinols to the unsaturated compounds VII is carried out with agents such as thionyl chloride, phosphorous oxychloride, phosphorous tribromide, sulfuric acid, oxalic acid, hydrochloric acid, etc. The choice of reagents and reaction conditions for obtaining the unsaturated compounds of Formula VII is determined by the nature of the quantities R and R The methanederivatives of type VIII are obtained by reduction of the unsaturated compounds VII by known methods for the 'hydrogenation of ethylene compounds.

With the exception of the alkyl and cycloalkyl types, the piperidine compounds VI can be made by the following alternate method which employs as intermediate the pyridine derivatives IX. The latter compounds can be obtained from the corresponding carbinols (I. A. C. S. 70, 3999 (1948); I. A. C. S. 71, 887 (1949)) by replacement of the hydroxyl group by halogen (thionyl chloride) followed by reductive dehalogenation using Zinc and acetic acid or any one of several catalytic procedures. The pyridine compound, on oxidation with potassium permanganate, yields the keto compounds X (I. A. C. S. 72, 2722 (1950)) which are then transformed into the tertiary scarbinols XI by the same procedures used for the conversion of V to V1. High'pressure catalytic hydrogenation of simultaneously reduces the pyridine ring, dehydrates the resulting piperidine carbinols (XII) and saturates the newly formed double bond ofXIII to yield the methane derivative XIV.

Using the N-alkylpiperidinecarboxylic acids III in the form of the ethyl or methyl esters in the conventional Grignard reaction with, e. g., an aryl, aralkyl, heterocyclic,

cycloalkyl or alkyl magnesium halide, the compounds of the general formula are obtained wherein R and R are the same. The reaction is illustrated by the following" from isonipecotic equation for the dipheny-l compound acid:

' The invention will be further described by way of the following examples, which are, however, presented only by way ofillustration and not as indicating the limitations of the invention:

EXAMPLE I Phenyl- (Z-pyridyl (N -methyl-4-piperidyl carbinol piperidyl)carbinol and 70 cc. of

p with cooling, excess 25% crude product may be purified by washing with cold, absolute ethanol.

The reduction also may be effected by dissolving isonicotinic acid in excess concentrated hydrochloric acid, evaporating the solution to dryness and reducing the hydrochloride salt in aqueous solution with platinum oxide catalyst.

N-methylisonipecotic acid hydrochloride: To 185 g. of

% formic acid in a one liter flask cooled in an ice bath is added 109 g. of isonipecotic acid hydrochloride, followed by 165 cc. of 37% formalin solution. The mixture is heated and stirred overnight, the solution then concentrated to dryness in vacuo, leaving a slightly gummy,

white residue. The latter is dried in a vacuum desiccator over phosphorus pentoxide and recrystallized from absolute ethanol, M. P. 225-226 C.

4-benzoyl-N-methylpiperidine: To 17.5 g. of N-methyL isonipecotic acid hydrochloride, in a 500 cc., three-necked flask fitted with a stirrer, dropping funnel and reflux con- 1 denser, is added dropwise cc. of thionyl chloride. The mixture is'refluxed and stirredfor twojhours and the excess thionyl chloride removed in vacuo. The flask is then cooled in an ice-salt bath and cc. of dry benzene added. To the stirred mixture, 77 giof anhydrous aluminum chloride is added during 30 minutes. The reaction mixture is allowed to warm to room temperature, stirred, and refluxed for 18 hours and poured on ice-hydrochloric acid. The benzene layer is extracted with 15% hydrochloric acid and the aqueous acid layers made allc-aline with 50% sodium hydroxide solution. The oil which separated is extracted with chloroform, the chloroform extracts dried over sodium sulfate, filtered; and, after removing the solvent, the residue is fractionated, B. P. 122 125 C./0.51 mm.

A solution of butyllithiumiis prepared in ether at 10 C. by reacting 1 g. of lithium, 100' 'cc. of anhydrous ether and 9.6 g. of dry butylbromide in a nitrogen atmosphere according to the directions of Gilman et al., J. A. C. S. 71, (1949.). The solution of butyllithium is cooled to -40 C. and 11.06 g. of 2-bromopyridine is added dropwise with stirring and the solution stirred for 30 minutes. Then 10.2 g. of 4-benzoyl-N-metliylpiperidine in 50 cc. of ether is added drop-wise and the reaction mixture allowed to warm to room temperature slowly and then stirred for an additional seven hours. The mixture is poured on ice and hydrochloric acid, the aqueous phase separated and then made alkaline. The base is taken up in ether and the ether extracts dried. After removal of the solvent, a white solid remains. Recrystallized from benzene, MI. P., ]22

123 C. Recrystallization from n-hexane raises the melting point to 125 C.

EXAMPLE Ia Phenyl-(Z-pyridyl)-(N-melhyl-4-piperidylidene)methane A mixture of 11 g. of phenyl-(Z-pyridyl)-(N-methyl-4- thionyl chloride is refluxed on the steam bath for two-ten hours. The excess thionyl chloride is removed in vacuo,.20 cc. of dry benzene added and the solvent distilled in vacuo to remove traces of thionyl'chloride. To-the oily residue is added slowly, sodium hydroxide solution. The product is then warmed on the steam bath with stirring for one hour and the oil taken up in benzene, dried, treated with activated carbon, filtered and concentrated todryness.

Alternatively, a mixture of one part of the piperidyl carbinol and six parts of 85% sulfuric acid is heated at C. for 30 minutesf The solution is poured on cracked ice, made basic with dilute sodium hydroxide and the oily layer extracted with ether. are washed, dried, and after removing the solvent, the residue is distilled in vacuo.

EXAMPLE II (p-Chl0rophenyl) (2-pyridyl) -(N-methyl-4- piperidyl) carbinol 4 (p-chlorobenzoyl) N-methylpiperidine.-Tweutyfive grams of N-methylisonipecotic acid is converted to the acid chloride and reacted with 394 g. of chlorobenzene and 114 g. of anhydrous aluminum chloride as i in Example I.

The excess chlorobenzene is removed by steam distillation and the acidic residue extracted'with The ether extracts chloroform and the sol-vent removed by distillation. The residue solidifies and is triturated cold petroleum ether, M. P. 118-119" C. .Rccrystallized from n-hexane, M. P. 124 C.

Conversion to .the carbinol is carried out as described for the corresponding phenyl compound of Example I. The product is obtained :as a viscous yellow oil, B. P. 223-225 C. (,5 mm.).

EXAMPLE .III

Diphenyl-(N-m ethyl-4-piperidyl) carbinol To a Grignard solution prepared from 4.9 g. of magnesium, 100 cc. of ether and 31.4 g. of dry bromobenzene is added 18.5 g. of 4 benzoyl-N-methylpiperidine in 200 cc. of dry ether. The reaction mixture is heated with stirring for four hours on the steam bath and then decomposed. The organic layer is separated and the aqueous layer extracted with benzene. The combined organic extracts are concentrated and the residue, diphenyl (N-methyl 4 piperidyl) carbinol, recrystallized from benzene-petroleum ether, M. P. l30l3l C. The Grignard complex may also be decomposed with ice and hydrochloric acid and the insoluble hydrochloride of the carbinol isolated directly.

EXAMPLE IIIa Diphenyl- (N-methyl-4-piperidylidene methane The carbinol may be converted to the unsaturated compound as described in Example Ia. Alternatively, the carbinol can be dehydrated with 60% sulfuric acid. In general, to one part of the carbinol there -is added parts of 60% sulfuric acid. The mixture after heating for six hours is poured onto crackedice, the solution made alkaline with dilute sodium hydroxide and the oily basic layer extracted with ether. extracts after washing with water aredried over sodium sulfate, and after removing the ether, the residue is distilled in vacuo, M. I. 52-53" .C.

Alternatively, a solution of 40 g. of (4-pyridyl)-diphenylcarbinol (prepared as shown in the equation in column 3, lines 10 to 52) in 10.0 ml. of dimethyl sulfate is heated on the steam bath for one hour. The dark brown solution is diluted with 500 cc. of benzene and the lower dark brown oily layer is separated and dissolved in 150 cc. of absolute ethanol. solution is reduced, at 50 lbs. hydrogen pressure with 1.5 g. of platinum oxide catalyst until the theoretical amount of hydrogen is absorbed. The catalyst is filtered off, the filtrate concentrated and the residue dissolved in 300 ml. of water. Addition of dilute sodium hydroxide gives a viscous dark oil which is extracted with benzene and after removal of the benzene in vacuo, the residue is dissolved in 300 cc. of 60% sulfuric acid. The resulting acid solution is heated for six ,hours on the steam bath and poured onto a mixture of ice and water. The resulting aqueous solution. is made alkaline with sodium hydroxide. The liberated oil is extracted with ether and after drying the ether solution and removing the ether, the residue is distilled. The product (N-methyl-4- piperidylidene)-l,l-diphenylmethane obtainedis identical with that secured by the foregoing procedure.

In place of dirnethyl sulfate, the pyridyl carbinol can be quaternized with methyl iodide, methyl bromide, methyl chloride, methyl-p-toluene sulfonate and other similar reagents. In place of platinum oxide catalyst there can be used Raney nickel at slightly higher pressures, palladium on carbon, platinum black and other similar catalytic materials.

EXAMPLE IV (p-Chlorophenyl)-phenyl-(N-methyl-4- piperidyl) carbinol This carbinol is prepared by reaction of 4-(p-chlorobenzoyl)-N-methylpiperidine with phenylmagnesium bromide as in Example vII. M. P. 142 C. from n-hexane.

The ether 7 The resulting EXAMPLE -v Phenyl-(Z-pyridyl) -(N-methyl-4-piperidyl)- carbinol hydrochloride The hydrochloride is prepared in the conventional manner from the carbinol of Example I and anhydrous hydrogen chloride in absolute ether. The melting point of the .crude hydrochloride is -90 C. It may be purified by recrystallization from a mixture of absolute alcohol and ether.

EXAMPLE v1 Phenyl-(Z-pyridyl) (N-methyl-4-piperidyl)- carbinol methiodide This quaternary salt is prepared from the carbinol of Example I and methyl iodide in the usual manner. The methiodide is a white, crystalline compound melting at 223.5224.5 C.

EXAMPLE VII Diphenyl-(-N-methyl-4-piperidyl) carbinol hydrochloride This hydrochloride is prepared in the conventional manner from the carbinol of Example III and anhydrous hydrogen chloride. The crude hydrochloride melts at 252 C. and after several recrystallizations from absolute alcohol'and ether mixture, an analytically pure sample melts at 290 C.

EXAMPLE VIII (p-Methoxyphenyl)-(2-pyridyl)1Nmethyl-4- piperidyl) carbinol The compound of this example is prepared as described for the unsubstituted compound of Example 1, except that anisole is used in place of the benzene in the Friedel- Crafts reaction. The 4-(p-methoxybenzoyl):N-methylpiperidine is obtained as a pale yellow liquid boiling at 136-139 C. (2 mm.). Reaction of this ketonic material with 2-pyridyllithium proceeds as described for the unsubstituted compound.

EXAMPLE IX Phenyl-(p-methoxyphenyl) (N-methyl-4 piperidyl) carbinol This compound is prepared in accordance with the procedure of Example I substituting pmethoxybromobenzene for the 2-bromopyridinein the lithium reaction. B. P. 202-209 C. (2 mm.); M. .P. 128-129" C.

EXAMPLE X Diphenyl-(N-methyl 4 piperidyl) carbinol methiodide This salt is prepared fromJthe free base of Example III and methyl iodide, M. P. 266-267 C.

EXAMPLE XI 7 Phenyl-cyclohexyl-(N-methyl-4 piperidyl) carbinol To a solution of cyclohexyl magnesium chloride (32 g. of chlorocyclohexane and -6.5 gjmagnesium) in 500 cc. of ethyl ether, there is added 27 g. of N-methyl-4-benzoylpiperidine. Following the addition, the mixture is re fluxed on the steam bath for four hours and after standing overnight is decomposed by pouring into a mixture of ice and hydrochloric acid. The tertiary base whichseparates is obtained in the form of the hydrochloride and in this crude state the hydrochloridemelts at 203-205 C. The crude hydrochloride is dissolved in water,-the'solution made alkaline with 50% NaOH and the oil which separates is extracted with ether. The ether extracts are evaporated and the residue is crystallized from- -,hexane or benzene, .144-l45 C. I

piperidine and Z-bromothiophene. M. P. 141-142" C. after recrystallization from ethyl alcohol.

EXAMPLE XIV Phenyl-(Z-thienyD (N-methyl-4-piperidyl)carbinol hy- 1. I drochloride V Thiscompound is'prepared from the carbinol of Example XIII and anhydrous hydrogen chloride, M. P. 238- 239' C.

EXAMPLE XV 'Di'p'henyl (N-methyl-4-piperidyl)carbinol Diphenyl-(N-methyl-4-piperidyl)carbinol may also be prepared in the following manner: To a solution of phenyl-magnesium bromide (prepared from 10.1 g. of

magnesium and 66 g. of bromobenzene) in 100 cc; of"

ether, is added 22 g. of methyl-N-methylisonipecotate in 100cc. of toluene. After heating for two hours on the steam bath, the reaction mixture is poured onto ice and dilute hydrochloric acid. The white solid is filtered and dissolved in hot water. The resulting solution is made basic with dilute sodium-hydroxide, the liberated oil is extracted with chloroform, the chloroform layer is dried and concentrated. The carbinol is obtained as a white crystalline solid, which melts at 130-131 C.

EXAMPLE XVI' Di-(2-thienyl)-(N-ethyl-4-piperidyl)carbinol This carbinol is prepared from the ethyl ester of N- ethyl-isonipecotic acid and Z-thienyl magnesium bromide in accordance with the procedure of the preceding example. The compound is obtained as a white crystalline solid which on recrystallization from ethanol melts at 120-121? 7 EXAMPLE XVII 'Phenyl-benzfl-(N-methyl-4-piperidyl)carbinol This carbinol is prepared from N-methyl-4benzoyl piperidine and benzyl magnesium chloride in the conventional Grignard reaction. The carbinol is obtained as a white crystalline solid melting at 116-117 C.

EXAMPLE XVIII Phenyl-benzyl (N-methyl-4-piperidyl)carbinol hydro,-

chloride This compound is prepared from the carbinol of the previous example and anhydrous hydrogen chloride, M. P. 244-245 C.

EXAMPLE XIX Phenyl(n-prbpyl)-(N-methyl-4-piperidyl) carbinol 8 EXAMPLE Phenyl-isoprop yl-(N-methyl-4-piperidyl) carbinol This compound is prepared as described for 'thecompound of Example XIX using isopropyl magnesium bromide, B. P. l30-135 C./12 mm. 1

EXAMPLE XXII Diphenyl-(N-ethyl-4-piperidyl) carbir zol This compound is made by the procedure of Example XV wherein methyl-N-ethylisonipecotate is reacted with phenyl magnesium bromide. The carbinol is obtained as a white, crystalline solid, which melts at 93-94" C.

EXAMPLE XXIII Diphenyl- (N -is0propyl-4-piperidyl) carbinol From methyl-N-isopropylisonipecotate and phenyl magnesium bromide by the procedure of Example XV, M. P. 133-134 C;

phenyl magnesium bromide bythe procedure of Example XV, M. P. 190-191 C.

EXAMPLE XXV Dipheny l- (N -n-pr opyl-4-piperidyl) carbinol From methyl-N-propylisonipecotate and phenyl magnesium bromide bythe procedure of Example XV, M. P. -126? C.

. EXAMPLE XXVI Diphenyl-(N-is0butyl-4-piperidyl)carbinol From methyl-N-isobutylisonipecotate and phenyl magnesium bromide by the procedure of Example XV, M. P. 136-137 C.

EXAMPLE XXVII y Di-(p-methoxyphenyl)-(N-methyl-4-piperidyl)carbinol From methyl-N-methylisonipecotate and p-methoxyphenyl magnesium bromide by the procedure of Example XV, M. P. 161-162 C. v

EXAMPLE XXVIH Di-(cyclohexyl)-(N-methyl-4-piperidyl)carbinol From methyl-N-methylisonipecotate and cyclohexyl magnesium bromide by the procedure of Example XV, M. P. 126-127 C.

EXAMPLE XXIX Phenyl-ethyl-(N-methyl-4-piperidyl)carbinol From the 4-benzoylN-methylpiperidine of Example I and ethyl magnesium bromide by the procedure of Example XIX, P. 108-109 C. 7

EXAMPLE XXX Ph enylm-chloropher lyl (N -methyl4-piperidyl carbinol By the procedure of Example XXIXsubstituting mchlorophenyl magnesium bromide for ethyl magnesium bromide, M. P. -136" C.

EXAMPLE XXXI magnesium bromide, is substituted for ethyl magnesium bromide, B..P. 164-167 C. (1.n1m.). s

9 EXAMPLE XXXIH Phenyl-(n-butyl) -N-methyl-4-piperidyl(carbin0l) By the procedure of Example XXIX wherein n-butyl magnesium bromide is substituted for ethyl magnesium bromide, 140-145 C. (3 mm.).

EXAMPLE XXXIV Phenylisobutyl-(N-methyl-4-piperidyl) carbinol By the procedure of Example XXIX wherein isobutyl magnesium bromide is substituted for ethyl magnesium bromide, M. P. 112-113" C.

EXAMPLE XXXV Phenyl-(A -cyclohexenyl) (N-methyl-4-pipridyl) carbinal By the procedure of Example XXIX substituting A cyclohexenyl magnesium bromide for ethyl magnesium bromide, B. P. l76182 C. (2 mm.); M. P. 104l05 C.

EXAMPLE XXXVI Phenyl(n-propyl) -(N-ethyl-4-piperidyl)carbinol The requisite intermediate, 4-benzoyl-N-ethyl-piperidine, is prepared from N-ethylisonipecotic acid hydrochloride and benzene with aluminum chloride in accordance with the procedure of Example I. The resulting 4- benzoyl-N-ethyl-piperidine is then treated with n-propyl magnesium bromide in accordance with the procedure of Example XXIX. The resulting carbinol is a pale yellow liquid boiling at 144-147" C. (1 mm.).

EXAMPLE XXXVII Phenyl -(Z-thienyl)-(N-ethyl-4-piperidyl) carbinol EXAMPLE XXXIX p-Methoxyphenyl-(n-propyl) -(N-methyl-4-pipefidyl) carbinol From 4-(p-methoxybenzoyl) -N-methylpiperidine and npropyl magnesium bromide, B. P. 165-170 C. (2 mm.).

EXAMPLE XL Phenyl-(n-propyl)-(N-isopropyl-4-piperidyl) carbinol From 4-benzoyl-N-isopropylpiperidine and n-propyl magnesium bromide, B. P. 143-153 C. (0.5 mm.).

10 Of particular utility for medicinal purpose are the piperidylidene compounds of the general formula R Rs In general, enhancement of the antiacetylcholine, ganglionic and parasympathetic blocking activities is achieved by forming the quaternary salts such as the methiodide, methochloride, methobromide, methosulfate, ethiodide, ptoluenesulfonate, etc., of the tertiary nitrogen atom. The quaternary salts of the piperidylidene compounds, for example, diphenyl-(N,N-dimethyl-4-piperidylidene)methane methylsulfate, are particularly advantageous in the control of gastric secretion and gastric motility in ulcer patients. In addition to the quaternary salts, acid addition salts such as the hydrochloride, tartarate, maleate, citrate and salicylate of the piperidine compounds of the general formula, for example, phenyl-(n-propyl)-(N- methyl-4-piperidylidene)methane citrate, have also been found to be efiective. The latter salts are particularly useful in those cases Where solutions of the amines of the invention are to be used.

This application is a division of our application Serial No. 242,438, filed August 17, 1951, which is a continuation-in-part of our application Serial No. 199,364, filed December 5, 1950.

We claim:

1. Piperidyl carbinols of the group consisting of compounds of the general formula ReferencesCited in the file of this patent FOREIGN PATENTS Great Britain Apr. 6, 1949 OTHER REFERENCES Tilford et al.: Iour. Am. Chem. Soc., vol. 70, pp. 4001- 09 1948 

1. PIPERIDYL CARBIONOLS OF THE GROUP CONSISTING OF COMPOUNDS OF THE GENERAL FORMULA 